Dimensioning system

ABSTRACT

The present invention determines the dimensions and volume of an object by using a novel 3-D camera that measures the distance to every reflective point in its field of view with a single pulse of light. The distance is computed by the time of flight of the pulse to each camera pixel. The accuracy of the measurement is augmented by capture of the laser pulse shape in each camera pixel. The camera can be used on an assembly line to develop quality control data for manufactured objects or on a moving or stationary system that weighs as well as dimensions the objects. The device can also ascertain the minimum size of a box required to enclose an object.

RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser.No. 60/679,579 filed May 10, 2005 and incorporated herein by reference.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention is a dimensioning system that rapidly measures thedimensions of the surface of any object having any size and shape. Notonly can the dimensioning system determine the dimensions of box-likeobjects, but it can also determine the dimensions of irregular-shapedobjects such as automobile tires on a conveyor belt.

B. Description of the Prior Art

In the packaging industry, the cost of shipping often depends upon boththe dimensions of an object and its weight and the procedure forassessing the shipping cost is called dimming. Because of the highvolume of packages shipped, errors are often made in calculating thecost. The proposed invention would perform this task automatically withhigh accuracy for each package. Even irregularly shaped packages couldbe rapidly measured. The 3-D object information would be translated intothe relevant shape parameters and then combined with the package weight,if necessary, to compute the shipping cost from existing rate schedules.

A similar dimensioning procedure can be applied to manufactured objectson an assembly line. Acceptance or rejection can be determined byautomatically comparing an object with a digitally stored 3-D referenceshape. In addition, the invention can ascertain the minimum sized boxneeded to enclose an object on a conveyor belt. This application isuseful if the conveyor is transporting many different objects each ofwhich will be packaged individually.

The present invention is a 3-D camera system using, in part, the 3-Dimaging technology disclosed in Stettner et al, U.S. Pat. Nos.5,446,529, 6,133,989 and 6,414,746 that provides with a single pulse oflight all the information of a conventional 2-D picture along with thethird dimensional coordinates. It furnishes the 3-D coordinates of everyreflective point in its field of view. The system is mechanically andoptically configured so it is useful in assembly-line machine-visionapplications in which the size and shape of objects must be rapidly andaccurately established.

Several methods of ascertaining the dimensions of an object and theminimum size box needed to enclose objects on a conveyor belt have beendeveloped. However, the prior art requires many light pulses to scan anobject's surface with a mechanical mechanism while the present inventionobtains all dimensions by simultaneously viewing the entire surface witha single light pulse and no moving components.

U.S. Pat. No. 6,177,999 discusses an optical scanning device whichmeasures the height of a point on the object by directing the reflectedlight onto a linear CCD array as the object is swept past the device ona conveyor belt. The invention is contrived so that the height of thepoint corresponds to a unique pixel on the CCD. The object's contoursare thus measured one point at a time.

U.S. Pat. No. 6,091,905 establishes the distance to an object byrecording the total radiant energy reflected from an object during aspecific length of time. A pulse of light is emitted having a pulsewidthequal to the time required for light to travel from the camera to thefarthest object of interest in the scene being viewed and return to thecamera. The camera observes the reflected light only during thisinterval. Nearby objects start reflecting earlier than farther objectsand hence deliver more radiant energy to the camera during theobservation interval.

U.S. Pat. No. 5,193,120 employs a video camera to image an objectilluminated by many parallel lines of light simultaneously. The object'sprofile is enhanced by viewing the reflected light at an angle. Thethree-dimensional aspect of the object is derived from the image of thelines of light and the geometrical properties of the imaging system.

The system in International Publication Number WO 94/27166 calculatesthe height of a point on an object by measuring the time of flightrequired for a light beam to reflect back to the device from a point onthe object. The invention moves above the object and establishes theminimum box size after many reflections.

U.S. Pat. No. 4,758,093 relies on a triangulation technique to find thesurface contours of an object.

SUMMARY OF THE INVENTION

The present invention is comprised of a novel 3-D camera that measuresthe distance to every reflective point in its field of view with asingle light pulse. In this application, “an object” can mean a singleobject or multiple objects. Using a lens, the camera images the objectilluminated by the light onto a pixilated, electronic light sensitivedetector called a focal plane array. The optics for collecting thereflected light may be a refractive telescope or reflective telescope.Each pixel converts the light into an electronic signal whose magnitudeis sampled in time and stored in memory within the pixel. Each pixelalso contains a clock that reports the time at which the samples aretaken. This information is read out from the array into a dedicatedcomputer that assesses when the light pulse arrived at each pixel and,hence, the elapsed time between the emission of the light and itsreception. The measures of distances from the camera to everything inits field of view is then computed with the known speed of light or anyother parameter by which the distances is determinable. The output ofthe 3-D camera is a three-dimensional image of the illuminated object,obtained from the measures of distances performed by the camera.

One objective of the invention is to measure the size, volume and weightof an object to compute accurately the cost of packaging or shipping.Another objective is to measure an object for quality control duringmanufacturing. A third objective is to find an object's dimensions tocalculate the minimum size box needed to contain it. A fourth objectiveis to measure the dimensions of a large object as in surveying.

The camera furnishes a metrically accurate three-dimensional picture ofthe object characterized by a conventional two-dimensional image towhich the third dimension is quantitatively added. Two such cameraslocated with the object between them will view all sides. Alternatively,if the object is resting on a plane surface such as a conveyor belt thedimensions viewed by one camera may be sufficient for quality controland packaging information. Objects with complex surfaces containingrecessions may require that pictures be taken from additional positionsif precise rendering of these features is needed.

Among the advantages of this device is its mechanical simplicity, thespeed with which it can obtain data and its ability to measure objectsof any size. Similar inventions require many light pulses to scan anobject's surface with a mechanical mechanism while the present inventionobtains all dimensions by simultaneously viewing the entire surface witha single light pulse and no moving components. Another advantage of thedevice is the enhanced third dimension accuracy stemming from samplingthe reflected light to determine the returning pulseshape. Similarinventions ascertain the arrival time from the peak of the return signalor some other characteristic without making use of the detailedpulseshape information. The present invention is a staring laser radarfor use in dimensioning systems.

Other advantages and uses of the invention will be apparent to thoseskilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective drawing of the dimensioning system of thepresent invention measuring the dimensions of an object on a conveyorbelt. The dimensioning system is comprised of a light source 4 a, anovel 3-D camera 5, and a sampler/digitizer 6 which monitors thepulseshape of the light produced by 4 a;

FIG. 2 shows the novel 3-D camera denoted by the number 5 in FIG. 1;

FIG. 3 shows the focal plane array denoted by the number 8 in FIG. 2;

FIG. 4 is a block diagram of the electronic circuit in the integratedelectronic circuit chip (the readout) denoted by the number 10 in FIG.3;

FIG. 5 is a block diagram of the electronic circuit on the printedcircuit board denoted by 12 in FIG. 2;

FIG. 6 is an alternative embodiment of the novel 3-D camera denoted bythe number 5 in FIG. 1;

FIG. 7 is an alternative embodiment of the focal plane denoted by thenumber 8 in FIG. 3;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments are described with reference to the figureswhere like numbers denote the same elements.

The present invention, depicted in FIG. 1, is a dimensioning system 1designed to measure the size and dimensions of any object. It iscomprised of a pulsed light source 4 a, a beam shaping element 4 b (asystem to shape the projected light), a 3-D camera 5, and aphotodiode/sampler 6. These latter four components are usually includedin a single enclosure but are exposed here for clarity. In the figure,the object being dimensioned 3 is supported a conveyor belt 2.

The components of the 3-D camera 5 are shown in FIG. 2. They are a lenssystem 7 which creates a real image of the object 3 on a focal planearray 8 and the circuit board 12 that generates the electrical signalsneeded to operate the focal plane array 8 and also process the data.

FIG. 2 indicates the focal plane array 8 is composed, in one embodiment,of a light sensitive detector array 9 and an integrated electroniccircuit chip called the readout array 10. FIG. 3 indicates the detectorarray 9 and the readout 10 are divided into pixels 13 and correspondingpixels (14 a and 14 b) on the readout array 10 and detector array 9 areelectrically connected by a metallic bump 11. The pixel 14 a on thereadout array 10 is referred to as a unit cell and its circuitry is unitcell electronics.

The unit cell electronics 14 a is diagrammed on FIG. 4. Each pixel 13contains an input amplifier 15, a triggering circuit 21, a delay circuit22, a shift register 19, a counter 23, and several switches 16 eachconnected to its own memory cell 17. Whenever the clock 18 (may not belocated within the pixel) goes high, the shift register 19 shifts. Thecounter 23 counts the number of times the shift register 19 shifts. Amultiplexer 24 connects to the unit cell output amplifier 25. Anadditional multiplexer located on the readout 10 multiplexes the unitcell 14 a signals to an output amplifier which drives the unit cell dataoff the readout 10. In an alternative embodiment, each pixel 13 does notcontain a triggering circuit 21.

A block diagram of the circuit board 12 is displayed on FIG. 5. Thefocal plane array 8 receives its power and the bias voltages needed torun it from power supply 27. The embedded computer 28 generates theclock signals for the focal plane array 8 and the memory 29. Data fromthe focal plane array 8 is partially (or completely) processed in theembedded computer 28 before being sent to the memory 29 and mastercomputer 30 which completes the processing, stores the results and maydisplay the acquired three-dimensional image. The master computer 30also permits the operator to communicate with the circuit board 12 and,indirectly, the focal plane array 8.

FIG. 6 illustrates an alternative embodiment of the electronic camera 5.A lens system 7 creates an image of the object 3 which is focused bymeans of the beamsplitter/mirror 32 on a focal plane array 8 and aconventional two-dimensional imaging device 31 such as a CCD array or atwo-dimensional CMOS focal plane array. The two-dimensional focal plane31 has sufficient resolution to read printed information on the object 3such as a label or a coded package number.

In operation objects 3 may be moving along a conveyor belt 2. Lightpulses are emitted from the light source 4 a through the beam shapingelement 4 b, either at programmed time intervals or in response to thedetection of an object on the conveyor belt 2 by a simple mechanism suchthe breaking of a continuous light beam by the object. Typically thepulsed light source 4 a is a laser. In addition to a pulsed laser, alaser diode or a monoblock laser may be used as the pulsed light source4 a. The beam shaping element 4 b may be an optical beam expander (beamexpansion optics) or it may be a diffuser. A desirable characteristic ofthe diffuser is that the light may be efficiently shaped to be the sameas the focal plane array 8. The diffuser may produce a rectangular beamthat has the same shape as the detector array 9. The pulsed lightstrikes the object 3 at many points on its surface, is reflected fromthe object 3, is collected by the lens 7, and focused on the focal plane8. This sequence of events is very similar to an ordinary 2-D digitalcamera used with a flash bulb. The difference is that the 3-D camera 5counts time in each of its readout array pixels, 14 b, on its focalplane 8 as wall as generating other data which can be used to accuratelycalculate the distance to each point on the object 3 associated witheach pixel 13. Generating the range data starts with detecting andsampling, in the photodiode/sampler 6, the outgoing laser pulse to theobject 3. This essentially provides both a time zero reference for allthe pixels and a laser pulse shape reference. If the laser pulse shapesare stable or high range accuracy is not necessary, sampling theoutgoing pulse is not necessary. The reflected light generates a currentin each detector pixel 14 b, which enters the input amplifier 15 of eachdetector's unit cell electronics 14 a. The bias voltages of the inputamplifier 15, as most of the other components in each unit cellelectronics 14 a, are generated by the circuit board electronics 12.

The input amplifier 15 either amplifies the electrical signal currentdirectly, as a current amplifier, or converts the electrical signal to avoltage as a resistive transimpedance amplifier. The signal then usuallyenters two parallels networks. One of these networks is a triggeringcircuit 21, typically a Schmitt Trigger with Memory, which changes stateif the signal is large enough. This triggering function can be held fromoperating with a programmed signal from the circuit board electronics 12for multifunction applications. The hold can be programmed to bereleased after a defined count or time or it can be held indefinitely.In other single-function designs the triggering circuit need not bepresent saving silicon real estate. Typically when the triggeringcircuit 21 is used, a delay circuit 22 is also used to delay action ofthe trigger pulse arising form the triggering circuit 21. The delaycircuit 22 is typically programmed to have multiple values, which areselected through the circuit board electronics 12. The other outputamplifier 15 parallel network is connected to an analog memory, whichusually has more than one analog memory component 17. Typically eachanalog memory component 17 is a capacitor. If there are more than oneanalog memory component 17 the input to the analog memory is usuallysequenced between analog memory components 17 by means of a shiftregister 19, which controls the connection to the analog memorycomponents 17 through their associated switches 16. The shift register19 is driven by a clock 18, which can be either on chip (on the readoutarray 10 included in the peripheral circuitry 14 c) or off-chip. Anon-chip clock is preferable for high frequency sequencing and inpractice there are many choices of on-chip frequencies that can beselected though the circuit board electronics 12. If the input amplifier15 is a current amplifier then the signal is integrated on the analogmemory component 16; if the input amplifier 15 is a transimpedanceamplifier then the input signal is a voltage and is sampled by theanalog memory 17. Only three analog memory components 17 are shown inFIG. 4 although in the preferred embodiment the number is typically3-128. Typically the analog memory components 17 are continually cycledby the shift register so they are always sampling or integrating theinput until stopped by the triggering circuit 21 or stopped by aprogrammable counter located on the circuit board electronics 12 oron-chip in the peripheral circuitry 14 c. That is after all memory cellshave been filled the memory cells are overwritten as new data arrives.Consequently, the memory cells are always filled with the most recentlysampled waveform data. If the programmable counter, which halts theshift register 19, is on-chip it is programmed through the circuit boardelectronics 12.

In other embodiments of the unit cell electronics 14 a circuitry such asdelta reset circuitry or correlated double sampling can be implementedto reduce the noise in the analog signals.

In one class of operations the triggering circuit 21 automatically stopsthe shift register 19 when it senses the reflected laser pulse andthereby samples the returning reflected laser pulse shape. The returninglaser pulse contains information about the target. In this class ofoperations it is desirable to also have data representative of the timeit took the laser pulse to leave the camera, reflect from the target andreturn to the target. Thus the triggering circuit also stops a timingcircuit, which is part of the data output from the unit cell 14 a andwhich is eventually processed into a 3-D image. An analog timing circuitusing a ramp voltage and switched capacitor is taught in Stettner, U.S.Pat. No. 6,133,989 and a digital counter is disclosed in Stettner, U.S.Pat. No. 6,414,746 B1. FIG. 4 illustrates a digital counter design wherethe counter 23 increases by one bit after each cycle though the shiftregister 19. This design allows minimal use of silicon real estate forthe longest distances.

In another embodiment of the unit cell circuitry 14 a design the counter23 and the shift register 19 are run simultaneously by the same clock 18and the shift register 19 does not drive the counter 23. In this latterembodiment the triggering circuit 21 stops both the shift register 19and the counter 23 if the clock is not in each unit cell. In stillanother embodiment of the unit cell circuitry 14 a the clock 18 onlydrives the counter 23 and the counter controls the memory cells 17through a multiplexer, which is substituted for the shift register 19.In all embodiments utilizing a counter 23 the counter is read outthrough a shift register (not shown) which may be in the unit cell or inthe peripheral circuitry. Typically the clock 18 is many GHz to MHz for3-D imaging applications but can be as low as KHz for alternativetwo-dimensional imaging applications.

Once both the timing and pulse shape data is collected it is output fromthe readout array chip 10 for development into the 3-D data required forthe application. If the timing data is digital counter data it isdirectly output as illustrated in FIG. 4. If the timing data is ananalog signal representative of when the charging of a capacitor by avoltage ramp was stopped, then an output amplifier is used. The analogdata representative of the pulse shape is output from the unit cellelectronics 14 a through an output amplifier 25. However the analog datamust be first multiplexed by a multiplexer 24. Once the analoginformation is output from the unit cell electronics 14 a it is outputfrom the readout array chip 10 by an additional output amplifier locatedin its peripheral circuitry 14 c. Clock signals to output the data aregenerated on the printed circuit board 12.

Once the data from a laser pulse is output to the circuit boardelectronics, typically it is processed to provide an accurate arrivaltime, and hence an accurate range or third dimension, and processed tofind a peak signal. This data processing can occur in the embeddedcomputer 28 of the circuit board electronics 12, in the master computer30 or preprocessed in the embedded computer 28 of the circuit boardelectronics 12, and completed in the master computer 30. The processingalgorithms include a matched filter or least squares fit of the outgoinglaser pulse to the reflected pulse data. The outgoing pulse data can bedata collected from the photodiode/sampler 6 or, if the pulse-to-pulsepulse shape is stable enough, from stored data. Other parametersconcerning the object 3 characteristics, as represented in the reflectedlaser pulse shape can similarly be obtained.

After the 3-D shape of the object 3 has been determined it is combinedwith data representative of the color of the object, the temperature ofthe object 3, identification numbers on the object, obtained by other2-D cameras 31, in the master computer 30 to develop the informationrequired for the application. The camera generated information may becombined with digital object 3 weight information in the master computer30. This information could be used to compute shipping costs, adjustbillings, remove items from an assembly line etc.

In one embodiment, the light source 4 is a pulsed laser diode thatcreates a pulse with a pulsewidth of several nanoseconds. A very largeobject or an object at considerable distance from the camera may requirea more powerful pulse from a high power laser. One very usefulintermediate size laser is a monoblock (pseudo-monolithic laser with anintracavity optical parametric oscillator) described in U.S. Pat. No.6,373,865 B1

The photodiode/sampler 6 converts the outgoing light to an analog signalwhich is sampled, digitized and forwarded to the embedded computer 28and the master computer 30. The photodiode/sampler 6 monitors thepulse-shape, which is utilized in determining the arrival time of thereturning light. In one preferred embodiment the photodiode/sampler 6 iscomprised of a light sensitive photodiode, which responds to the lightpulse wavelength and a sampling circuit with memory. Accuracy of thetarget distance increases with sampling frequency. One way of increasingthe sampling frequency is to employ several light detectors, which aretimed so that the pulse collected, are at interleaved positions.Alternatively differing lengths of fiber optic cables can be used foreach of the light detectors, maintaining the same timing, so that thedetection will be out of phase in each detector. It is advantageous touse many detectors with the same phasing so that they can be averagedreducing the noise and increasing the accuracy of the captured outgoingpulse shape.

In one preferred embodiment, the light sensitive or photon detectorarray 9 (FIG. 3) is an array of P-intrinsic-N (PIN) or N-intrinsic-Pphotodiode fabricated on a single semiconductor chip. Fully depletingeach diode ensures that photoelectrons generated in a detector pixel 14b are conducted by the pixel's metallic bump 11 into the readout pixel(unit cell) 14 a closest to it. In another embodiment, the lightsensitive detector 9 is incorporated into the readout pixel 14 a itselfin a way known by those familiar with the art. This monolithic designeliminates the complexity of two chips (9 and 10) hybridized withmetallic bumps 11. In another preferred embodiment of the presentinvention the light sensitive or photon detector array 9 is an avalanchephotodiode (APO) array. These photodiode are normally operated at highervoltage than either a PIN or NIP photodiode and result in electronmultiplication or gain within the detector. This is an advantage fordetecting weak signals. The disadvantage is that noise is producedduring the gain process resulting in a noise factor, which will reducethe signal-to-noise ratio (SNR) for sufficiently strong signals. U.S.Pat. No. 6,555,890 B2 teaches that a PIN and APD can be produced incombination, in the same pixel, and selectively used depending upon thesignal strength circumstances, or, in other words an avalanchephotodiode can be made together with a corresponding ordinary PIN or NIPphotodiode so that either detector can be used to detect photons,depending on the circumstances and the signal-to-noise ratiorequirements. In another preferred embodiment of the current inventionthe light sensitive or photon detector 14 b is an APO combined with aPIN detector in the same pixel.

In another preferred embodiment of the current invention the focal planearray 8 with its two hybridized arrays 9 and 10 are incorporated in animage tube 33 (FIG. 7), wherein the actual light sensitive or photondetector 9 a is a photocathode. In this latter embodiment photons passthrough the window 37 and generate photoelectrons in the photocathode 9a. The photoelectrons are accelerated from the photocathode 9 a to thephoton detector array 9 except that under these circumstances thedetector array 9 collects the photoelectrons not photons; thephotoelectrons are amplified in the detector array 9 by impactionization. The advantage of this embodiment over the embodiment thatuses an APD is that the noise factor is greatly reduced, approachingone, and the amplification is much greater than the APD. Thus theamplified signal of an image tube results in a large SNR even it thesignal is large.

Yet other embodiments of the photon detector may be an InGaAs avalanchephotodiode, an avalanche photodiode made from a semiconductor material,a Digicon or an array of PIN or NIP semiconductor photodiodes. When thephoton detector is an array of photodiode detectors, each detector maybe electrically connected to the unit cell electronics on the readoutchip by conducting bumps.

The processing readout chip may be composed of bulk silicon and siliconon EPI (epitaxial layer) CMOS components, or it may be composed ofsilicon on insulator components.

The photon detector tube may be an image tube where the light isconverted to photoelectrons by a photocathode. The image tube photonamplification may be based on impact ionization of the photoelectrons ina semiconductor detector array or on impact ionization of thephotoelectrons in a PIN, NIP or avalanche photodiode detector array. Theimage tube amplification may be based upon amplification of thephotoelectrons in a microchannel plate and collection of thephotoelectrons by an anode array.

In another image-tube 33 focal plane array 8 embodiment the detectorarray 9 is replaced by an anode array and a microchannel plate, providesthe photoelectron amplification, and is inserted between thephotocathode 9 a and the anode array. In all image tube focal planearray 8 embodiments a single monolithic chip can be used withincorporates either the detector or anode feature in each readout pixelor unit cell. The advantage of the two-chip hybrid over the monolithicdesign is greater collection efficiency and more protection for thereadout electronics from high energy particle damage. In all the imagetube photon detection embodiments the electronic amplifier 15 mayrequire only a small gain permitting the system to be highly linear,with large bandwidth, which both simplifies and improves the accuracy ofthe data analysis. In all the image-tube 33 embodiments a magnetic fieldcan be imposed along the axis of the image tube decreasing the lateralmovement of the photoelectrons in their transit though the vacuum andthus increasing the spatial resolution. This later configuration iscalled a Digicon.

In one preferred embodiment the readout array 10 is an electronicintegrated circuit fabricated on a single piece of silicon. In anotherpreferred embodiment the readout array 10 is an electronic integratedcircuit fabricated with silicon on insulator (SOI) technology. In yetanother preferred embodiment the readout array 10 is an electronicintegrated circuit fabricated with silicon on EPI (epitaxial layer)technology.

It is very useful to adapt the processing readout chip to complete aprocessing cycle during a time interval of less than 20 ns and to resetin a time interval of less than 10 ns in preparation for the next lightsource pulse. The processing readout chip may also have a delta resetcircuit or correlated double sampling circuitry for enhanced signal tonoise ratio.

FIG. 4 is a block diagram of the electronic components of the readoutunit cell 14 a. In one preferred embodiment, sampling begins and thecounter 23 starts counting when the light pulse is emitted. Theamplifier output 20 is monitored by the trigger circuit 21 which outputsa signal to a delay circuit 22 when the amplifier output 20 reaches apre-specified magnitude. After a preset time delay, delay circuit 22stops the shift register, which terminates the sampling. A counter 23counts the number of times the shift register has shifted. In anotherpreferred embodiment, sampling is begun when a signal is input to thereadout from the circuit board 12. In another preferred embodiment theaction of the trigger circuit 21 is held and sampling is stopped when asignal is input to the readout from the circuit board 12 or the readoutarray chip peripheral circuitry 14 c.

In one embodiment the unit cell input amplifier 15 can be a resistivetransimpedance amplifier wherein the current from the detector pixel 14b is converted to a voltage and the sampling is voltage sampling andthere is not signal integration. In another embodiment the inputamplifier 15 can be a current amplifier wherein the current from thedetector pixel 14 b is amplified and/or conditioned; the sampling isstill voltage sampling but the signal is actually integrated on thememory 17. In both these embodiments the amplifier can be linear or maybe linear for part of its range and then non-linear for very largeamplitude signals. The non-linearity of the amplifier near the end ofits range serves to prevent amplifier saturation from near objects orhighly reflective objects.

FIG. 5 is a block diagram of the drive and output electronics circuitson the printed circuit board 12. The drive electronics furnishes thevoltages to supply power and biases 27 to the readout 9 and detector 10.All clock signals are generated by the embedded computer 28. Theseinclude the signals to initiate data acquisition, regulate raw dataoutput from the focal plane array 8, and set options such as the clockfrequency 18 and delay time 22. Some of the data analysis isaccomplished by the embedded computer 28 whose program is referred to asfirmware. In one preferred embodiment the embedded computer 28 is afield programmable gate array. The data and the results of the analysisinside the embedded computer 28 are stored temporarily in memory 29. Amaster computer 30 controls the circuit board, processes and stores thedata output to it and may displays a picture of the 3-D scene with dataoverlays from one or more two-dimensional focal planes 31 to enhance thediscrimination of the object 3 features. The program of the mastercomputer 30 is referred to as software.

In many applications information printed on the object such as labelsand bar codes must be read. In one embodiment this is done with ambientlight which makes a conventional, two-dimensional image on the focalplane array 8. Every memory cell 17 in a unit cell 14 a has this imagestored in it and it can be readout as a two-dimensional image before thelaser pulse data is collected. These two dimension images can be addedto increase the signal to noise ratio. In another embodiment, theambient light is supplemented by a flood light. FIG. 6 illustrates athird embodiment, which uses a second imager 31 (e.g. a charge coupleddevice or a conventional CMOS light integrating focal plane array for aninfrared focal plane array) to record the two-dimensional image. Theadvantage of this embodiment is that the two-dimensional focal plane,usually has a smaller pixel than the 3-D focal plane 8 and can thereforehave a much higher spatial resolution than the 3-D focal plane forreading small labels; this can reduce the cost of the overall system,and both the 2-D and 3-D images are generated simultaneously. Anotheradvantage of this latter embodiment is that the 2-D image can be a fullcolor image (or an infrared image) and can be digitally overlaid on the3-D image for enhanced feature identification. Typically the pulsedlight source is a laser with only one wavelength. The beam splitter 32reflects the pulsed light's wavelength to the focal plane array 8 andtransmits the visible light toward the second imager 31.

Many applications require the weight of the object to be measured. Inone embodiment this is accomplished by supporting the conveyor belt 2 ona scale (not shown) comprised of springs or piezoelectric actuators.

The distance to the target is

$D = {\frac{c}{2}\left( {T_{arrival} - T_{start}} \right)}$

where c is the speed of light in the medium, T_(start) is the time atwhich the pulse is emitted, and the counters start counting (or thevoltage ramp begins) and T_(arrival) is the time light arrives back atthe pixel. T_(arrival)−T_(start) is approximately the number of countsin the counter 23 multiplied by the clock 18 period. More accurately, itis the time elapsed between the emission of the pulse and the change ofstate of the Schmitt trigger plus the delay time metered by the delaycircuitry 22. This estimate may be improved by fitting the sampled pixelwaveform with the waveform of the outgoing pulse sampled by thephotodiode/sampler 6. If the noise is small, this technique can yieldT_(arrival) with an accuracy much smaller than the clock 18 perioditself.

The pulseshape fit may require correction of the outgoing waveform foramplitude, the orientation of the reflecting surface of the object, theindividual response of the pixel's amplifiers and the individualcharacteristics of each memory cell 17. The least squares algorithm ormatched filter algorithm may furnish the beet values of these parametersas well as the pulse's arrival time at the pixel. Error due toelectronic noise and random fluctuations of the transmitting medium andvariations in the outgoing waveform can be reduced by averaging datafrom many light pulses. An alternative embodiment of the readoutelectronics permits the averaging to be done on the readout array 10.

For many applications where a 3-D image of an object is required noknowledge of the position of the object is necessary by using thetriggering circuit 21 function in FIG. 4. The Schmidt Triggerautomatically stops the counter and shift register when it senses areturn pulse. However if the object is semitransparent and it isdesirable to obtain a 3-D image of both the outer and inner surfacesthere may not be enough Memory cells 17 to capture more than the returnfrom the first surface. Under these circumstances the Schmidt Trigger 21in FIG. 4 can be held and the clock stopped after a programmed time;this would allow two consecutive light pulses to capture informationboth from the transparent surface and the surface behind it. In anotherembodiment critical parts of the Readout unit cell circuitry in FIG. 4are repeated so that more than one consecutive return can be detectedwith a single laser pulse.

In an alternative embodiment several images are taken from slightlydifferent camera positions so that the image area viewed by each pixelis somewhat altered. The resulting increase in data will result in amore accurate assessment of the object's dimensions.

A single camera can only view part of an object. To view all sides, itis necessary to rotate the object, change the camera position or employtwo or more cameras. A system of mirrors can also be arranged to viewall sides with a single photograph.

Although the invention has been described in terms of particularembodiments, the embodiments are merely illustrative of an applicationof the principles of the invention. Numerous modifications may be madeand other arrangements may be devised without departing from the spiritand scope of the invention.

The invention claimed is:
 1. An optical dimensioning system with a fieldof view for measuring the dimensions of a reflective object positionedwithin said field of view, the system comprising: a pulsed light source;a beam shaping element for distributing power from said pulsed lightsource over said field of view; an optical sampler for sampling theoutput of said pulsed light source; an object positioning system; and a3D camera including: a lens system for collecting pulsed light reflectedfrom said object; a focal plane array having an array of light sensitivedetectors, each detector producing an electrical pulse response signalfrom an incident pulsed light signal, each of said light sensitivedetectors electrically connected by a metallic bump to a unit cellelectrical circuit of a readout array, wherein said readout array has aclock connected to an array of unit cell electrical circuits; andwherein each unit cell electrical circuit includes: an input amplifierwith an amplifier output connected to a plurality of switches, eachswitch connected to a memory capacitor; a logic element with a pluralityof sequenced outputs, each of said sequenced outputs connected to acontrol input of one of said switches, each sequenced output of saidlogic element adapted to turn one of said switches on and off upon atransition of said clock thereby producing an analog sample of saidelectrical pulse response signal; a counter connected to said logicelement for counting the number of said analog samples; a triggercircuit with an output connected to said logic element, to terminate theanalog sampling; and a multiplexer having a plurality of inputs; whereineach of said inputs is connected to a memory capacitor; and wherein saidmultiplexer has an output connected to a global multiplexer residing onthe periphery of said readout array; a supporting circuit board having apower supply connected to said focal plane array and applying power andbias voltages to said focal plane array.
 2. The dimensioning system ofclaim 1, wherein said logic element comprises a delay circuit and ashift register.
 3. The dimensioning system of claim 1, wherein saidoptical sampler is a photodiode.
 4. The dimensioning system of claim 1,wherein said optical sampler provides a time zero reference.
 5. Thedimensioning system of claim 1, wherein said optical sampler is adaptedto capture a laser pulse shape reference.
 6. The dimensioning system ofclaim 1, wherein said clock resides outside of said readout array onsaid circuit board.
 7. The dimensioning system of claim 1, wherein saidinput amplifier is a transimpedance amplifier.
 8. The dimensioningsystem of claim 1, wherein said analog samples capture the reflectedlaser pulse shape.
 9. An optical dimensioning system with a field ofview for measuring the dimensions of a reflective object positionedwithin said field of view, the system comprising: a pulsed light source;a beam shaping element for distributing power from said pulsed lightsource over said field of view; an optical sampler for sampling theoutput of said pulsed light source; an object positioning system; a lenssystem creating an image of said object at a focal plane of said lenssystem; and a focal plane array positioned in said focal plane, saidfocal plane array including an array of light sensitive detectors, eachdetector producing an electrical pulse response signal from an incidentpulsed light signal, each of said light sensitive detectors electricallyconnected by a metallic bump to a unit cell electrical circuit of areadout array, wherein said readout array has a clock connected to anarray of unit cell electrical circuits, and wherein each unit cellelectrical circuit includes: an input amplifier with an amplifier outputconnected to a plurality of switches, each switch connected to a memorycapacitor; a logic element with a plurality of sequenced outputs, eachof said sequenced outputs connected to a control input of one of saidswitches and adapted to turn one of said switches on and off upon atransition of said clock thereby producing an analog sample of saidelectrical pulse response signal; a counter connected to said logicelement for counting the number of said analog samples; a triggercircuit with an output connected to said logic element to terminate theanalog sampling; and a multiplexer having a plurality of inputs, andeach of said inputs connected to a memory capacitor, said multiplexerfurther having an output connected to a global multiplexer residing onthe periphery of said readout array; and a two dimensional imagingdevice.
 10. The dimensioning system of claim 9, wherein said lens systemfurther comprises a beamsplitter.
 11. The dimensioning system of claim9, wherein said two dimensional imaging device receives incident lightthrough said lens system.
 12. The dimensioning system of claim 9,wherein said two dimensional imaging device receives incident lightthrough a beamsplitter.
 13. The dimensioning system of claim 9, whereina 2D image from said two dimensional imaging device is overlaid on a 3Dimage from said focal plane array.
 14. An optical dimensioning systemwith a field of view for measuring the dimensions of a reflective objectpositioned within said field of view, the system comprising: a pulsedlight source; a beam shaping element for distributing the power fromsaid pulsed light source over said field of view; an optical sampler forsampling the output of said pulsed light source, an object positioningsystem; and a 3D camera including: a lens system for collecting pulsedlight reflected from said object; a focal plane array having an array oflight sensitive detectors, each detector producing an electrical pulseresponse signal from an incident pulsed light signal, each of said lightsensitive detectors electrically connected by a metallic bump to a unitcell electrical circuit of a readout array; and wherein said readoutarray has a clock connected to an array of unit cell electricalcircuits; and wherein each unit cell electrical circuit includes: aninput amplifier with an amplifier output connected to a plurality ofswitches, each switch connected to a memory capacitor; a logic elementwith a plurality of sequenced outputs, each of said sequenced outputsconnected to a control input of one of said switches and adapted to turnone of said switches on and off upon a transition of said clock therebyproducing an analog sample of said electrical pulse response signal; acounter connected to said logic element for counting the number of saidanalog samples; a trigger circuit with an output connected to said logicelement to terminate the analog sampling; and a multiplexer having aplurality of inputs, each of said inputs connected to a memorycapacitor, said multiplexer further having an output connected to aglobal multiplexer residing on the periphery of said readout array; asupporting circuit board having an embedded computer connected to saidreadout array, receiving 3D image data from said readout array, andperforming operations on said 3D image data.
 15. The dimensioning systemof claim 14, wherein said logic element comprises a delay circuit and ashift register.
 16. The dimensioning system of claim 14, wherein saidoptical sampler is a photodiode.
 17. The dimensioning system of claim14, wherein said optical sampler provides a time zero reference.
 18. Thedimensioning system of claim 14, wherein said optical sampler captures alaser pulse shape reference.
 19. The dimensioning system of claim 14,wherein said clock resides outside of said readout array on said circuitboard.
 20. The dimensioning system of claim 14, wherein said analogsamples capture the reflected laser pulse shape.
 21. An opticalsurveying system with a field of view for measuring the dimensions of areflective object positioned within said field of view, the systemcomprising: a pulsed light source; a beam shaping element fordistributing the power from said pulsed light source over said field ofview; an optical sampler for sampling the output of said pulsed lightsource, and producing an electrical time zero reference signal; and a 3Dcamera including: a lens system for collecting pulsed light reflectedfrom said object; a focal plane array having an array of light sensitivedetectors, each detector producing an electrical pulse response signalfrom an incident pulsed light signal, each of said light sensitivedetectors electrically connected by a metallic bump to a unit cellelectrical circuit of a readout array; and wherein said readout arrayhas a timing reference signal connected to an array of unit cellelectrical circuits; and wherein each unit cell electrical circuitincludes: an input amplifier with an amplifier output connected to atrigger circuit and to a timing circuit, said timing circuit using saidtiming reference signal to produce an elapsed time measurement outputindicating the elapsed time between said time zero reference signal anda terminating signal produced by said trigger circuit within said unitcell, said trigger circuit adapted to detect the presence of anelectrical pulse response signal, and having an output terminatingsignal which terminates the timing of the elapsed time measurement; anda unit cell output circuit adapted to output said elapsed timemeasurement, said unit cell output circuit further connected to a globalmultiplexer residing on the periphery of said readout array, and saidglobal multiplexer adapted to both select a unit cell output and providean elapsed time measurement as an output of said readout array; asupporting circuit board having an embedded computer connected to saidreadout array, said embedded computer receiving a plurality of unit cellelapsed time measurements from said readout array, and said embeddedcomputer performing digital processing on said plurality of unit cellelapsed time measurements.
 22. The surveying system of claim 21, whereinthe timing reference signal is a clock.
 23. The surveying system ofclaim 21, wherein the time zero reference signal is a pulse.
 24. Thesurveying system of claim 21, wherein the optical sampler is aphotodiode.